DIAMETER GROWTH AT THE STUMP 61 



2. Average the periodic growth and the diameter class of all trees of 



each class separately. (See Problem 16 for method.) 



3. Even off by a curve. 



4. Construct a table showing for each D.B.H. inch class: 



(a) The periodic growth as read from the table. 



(b) The periodic annual growth. 



(c) The number of years required to grow 1 inch. 



D. Discussion. 



1. Solve the following problem from the above table: 



If you are cutting to a 14-inch diameter limit, in how many years 

 will the 8-inch trees be ready to cut? Show how you derived the 

 result. 



PROBLEM 28. (Office.) The Transposing of a Table of Diameter 

 Growth at the Stump to Growth at D.B.H. 



Explanation. — Since for practical purposes all measurements of trees are 

 based on the D.B.H., outside of bark, the most valuable diameter growth 

 tables are those which show the growth at that point. For obvious reasons 

 it is in most cases impracticable to analyze trees at the D.B.H. The object 

 of this exercise is to construct a table showing the rate of growth at D.B.H, 

 outside of bark from analyses made at the stump (D.I.B.) 



Directions: 



A. Data Required. — D.B.H., complete stump analyses, and total ages. 



Use the same data (Series III) used in Problem 26. The curve for 

 average D.I.B. growth at the stump constructed in that exercise will 

 be taken as a basis for the work. 



B. Method of Procedure. 



1. Lay off a sheet of cross-section paper as in Problem 26, and transfer 



the average curve from that sheet to the new sheet by plotting the 

 values from the table made in Problem 26. Do not prick the points 

 through the paper as this often results in inaccuracies. Label this, 

 "Curve I, (D.I.B. Stump)." 



2. On this same sheet now draw Curve II to show the ratio between 



D.I.B. (stump) and D.B.H. (outside of bark) as follows: 

 (a) Let ordinates represent D.I.B. values as for Curve I. Now lay off 

 D.B.H. values as abscissa), the abscissa) to have the same value 

 (in number of spaces on the paper alotted to each unit) already 

 established for the ordinates; i.e., if one large space represents 

 2 inches on the ordinate axis, it shall also represent 2 inches on 

 the abscissa axis. These values may be placed directly below 

 the age figures. Be sure to label each set of figures. Confusion 



